@@ -86,6 +86,7 @@ const supportsSessionLifecycle = process.env.T3_ACP_SESSION_LIFECYCLE === "1";
 const supportsAcpMcp = process.env.T3_ACP_MCP_ACP === "1";
 const supportsHttpMcp = process.env.T3_ACP_MCP_HTTP === "1";
 const supportsV2Management = process.env.T3_ACP_V2_MANAGEMENT === "1";
+const failDeleteSession = process.env.T3_ACP_FAIL_DELETE_SESSION === "1";
 const advertisedAuthMethodId = process.env.T3_ACP_AUTH_METHOD_ID?.trim();
 const initializeAuthMethodId =
   advertisedAuthMethodId ?? (supportsSessionLifecycle ? "test" : undefined);
@@ -742,6 +743,9 @@ const program = Effect.gen(function* () {
   yield* agent.handleDeleteSession(() =>
     Effect.gen(function* () {
       yield* requireAuthentication();
+      if (failDeleteSession) {
+        return yield* AcpError.AcpRequestError.internalError("delete failed");
+      }
       return {};
     }),
   );
 
@@ -9,6 +9,7 @@ import { ProviderInstanceId } from "@t3tools/contracts";
 import { AcpRegistrySettings } from "@t3tools/provider-acp-registry/settings";
 import { describe, expect, it } from "@effect/vitest";
 import * as Effect from "effect/Effect";
+import * as FileSystem from "effect/FileSystem";
 import * as Schema from "effect/Schema";
 import * as EffectAcpErrors from "effect-acp/errors";
 
@@ -20,6 +21,7 @@ import {
   logoutAcpRegistry,
   normalizeAcpRegistryAuthMethods,
   normalizeAcpRegistryCommands,
+  probeAcpRegistryConfiguration,
 } from "@t3tools/provider-acp-registry/testing";
 import * as AcpRegistrySupport from "@t3tools/provider-acp-registry/server/AcpRegistrySupport";
 
@@ -379,6 +381,60 @@ describe("ACP Registry probe", () => {
     );
   });
 
+  it.live.each(["succeeds", "fails"] as const)(
+    "deletes its health-probe session when deletion is advertised and %s",
+    (deleteOutcome) =>
+      Effect.gen(function* () {
+        const fs = yield* FileSystem.FileSystem;
+        const directory = yield* fs.makeTempDirectoryScoped({ prefix: "acp-probe-delete-" });
+        const requestLogPath = NodePath.join(directory, "requests.ndjson");
+        const catalog = AcpRegistrySupport.AcpRegistryCatalog.of({
+          search: () => Effect.die("unused search"),
+          prepare: () => Effect.die("unused prepare"),
+          inspect: () => Effect.die("unused inspect"),
+          uninstallManagedBinary: () => Effect.die("unused uninstall"),
+          resolve: () =>
+            Effect.succeed({
+              agent: {
+                id: "mock-agent",
+                name: "Mock Agent",
+                version: "1.0.0",
+                description: "ACP probe cleanup test agent",
+                distribution: { npx: { package: "[email protected]" } },
+              },
+              distribution: "npx" as const,
+              spawn: {
+                command: "node",
+                args: [mockAgentPath],
+                env: {
+                  ...process.env,
+                  T3_ACP_V2_MANAGEMENT: "1",
+                  T3_ACP_REQUEST_LOG_PATH: requestLogPath,
+                  ...(deleteOutcome === "fails" ? { T3_ACP_FAIL_DELETE_SESSION: "1" } : {}),
+                },
+              },
+            }),
+        });
+
+        const result = yield* probeAcpRegistryConfiguration({
+          instanceId,
+          settings: decodeSettings({ agentId: "mock-agent" }),
+          cwd: process.cwd(),
+          environment: process.env,
+        }).pipe(Effect.provideService(AcpRegistrySupport.AcpRegistryCatalog, catalog));
+        expect(result.probe.ready).toBe(true);
+        expect(result.probe.sessionManagement.canDelete).toBe(true);
+
+        const requests = (yield* fs.readFileString(requestLogPath))
+          .split("\n")
+          .filter((line) => line.length > 0)
+          .map((line) => JSON.parse(line));
+        expect(requests.filter((request) => request.method === "session/delete")).toEqual([
+          expect.objectContaining({ params: { sessionId: "mock-session-1" } }),
+        ]);
+      }).pipe(Effect.scoped, Effect.provide(Layer.mergeAll(NodeServices.layer, NodeCrypto.layer))),
+  );
+
   it("distinguishes authentication failures from generic probe failures", () => {
     const advertised = normalizeAcpRegistryAuthMethods([
       { id: "grok-login", name: "Log in with Grok" },
 
@@ -45,6 +45,7 @@ const MAX_COMMAND_LINE_LENGTH = 2_048;
 const PROBE_TIMEOUT_SECONDS = 60;
 const PROBE_TIMEOUT = `${PROBE_TIMEOUT_SECONDS} seconds`;
 const COMMAND_ADVERTISEMENT_GRACE = "500 millis";
+const PROBE_SESSION_DELETE_TIMEOUT = "5 seconds";
 
 const boundedText = (value: string, maximumLength: number): string =>
   value.trim().slice(0, maximumLength);
@@ -419,6 +420,13 @@ export const probeAcpRegistryConfiguration = Effect.fn("AcpRegistryProbe.probeCo
         );
       }
       const started = startResult.success;
+      // Agents that persist sessions (OpenCode) would otherwise keep one empty session per probe.
+      // The runtime only sends session/delete when the agent advertises it.
+      yield* Effect.addFinalizer(() =>
+        runtime
+          .deleteSession(started.sessionId)
+          .pipe(Effect.timeoutOption(PROBE_SESSION_DELETE_TIMEOUT), Effect.ignore),
+      );
       yield* Deferred.await(commandsAdvertised).pipe(
         Effect.timeoutOption(COMMAND_ADVERTISEMENT_GRACE),
       );
 
@@ -18,6 +18,7 @@ export {
   logoutAcpRegistry,
   normalizeAcpRegistryAuthMethods,
   normalizeAcpRegistryCommands,
+  probeAcpRegistryConfiguration,
   type AcpRegistryAvailableCommands,
   type AcpRegistryLiveConfiguration,
 } from "./server/probe.ts";